Radon is a radioactive gas that occurs naturally, formed from radium decaying in rock and soil. It mainly enters the home via a process known as ‘advection’ where the gas moves from the ground to the lowest point of pressure inside the building. So the house is actually sucking the gas in. It also makes its way in through cavity walls, floor and wall cracks, gaps in the floor and around pipes. Research carried out by Public Health England and UCL finds that older homes with retrofitted insulation are likely to suffer increased levels of radon compared to those with no fabric energy upgrades. For example, the research found that double glazed windows had the largest association with indoor radon levels at 67%, compared to a property without the measure. It also found that loft insulation can increase levels by 47% and wall insulation by 32%. You can read the research paper here. The UK Radon Association reports that more than 2000 people die per year in the UK from lung cancer with direct links to radon exposure. You’ll find their useful guide here.